Fine-particle aggregate emulsion, process for producing such an emulsion, thermal recording media, coated paper and paint incorporating such an emulsion

A fine-particle aggregate emulsion comprises aggregate particles formed from a copolymer (a) composed of an unsaturated carboxylic acid and a vinyl monomer copolymerizable therewith, and a foreign polymer (b) formed by polymerization of a vinyl monomer differing in composition from that used in copolymer (a). The foreign polymer (b) is present in the form of particles having a diameter of 0.05 to 0.5 µm, the aggregate particles having a diameter of 0.2 to 3.0 µm. This fine-particle aggregate emulsion is useful in paints, paper coating and information recording media. The emulsion is prepared by preparing copolymer (a) by emulsion polymerization and neutralizing the resulting copolymer emulsion with alkali, adding the vinyl monomer for foreign polymer (b) to the neutralized emulsion, and emulsion polymerizing the resulting mixture using the neutralized emulsion as seed particles.